Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H,W = map(int, input().strip().split(' '))

maze = ['#'*(W+2)]
maze += ['#'+input().strip()+'#' for _ in range(H)]
maze.append('#'*(W+2))
maze_map = [[float('inf')]*(W+2) for _ in range(H+2)]
maze_map[1][1] = 1

# 幅優先
mem = [(1,1)]

while True:
  if len(mem) == 0: break
  x,y = mem.pop()
  for dx,dy in [(1,0),(-1,0),(0,1),(0,-1)]:
    if maze[y+dy][x+dx] == '.':
      if maze_map[y+dy][x+dx] > maze_map[y][x]+1:
        maze_map[y+dy][x+dx] = maze_map[y][x]+1
        mem.append((x+dx,y+dy))
        
if maze_map[H][W] == float('inf'):
  print(-1)
else:
  w = sum(m.count('.') for m in maze)
  print(w-maze_map[H][W])